OK, the tail panel on a `Cuda is painted Organosil Black (rough textured Black).
Standard Barracuda has body colour on the tail panel except when coded with M88 (`Cuda Trim) then it also would be Organosil Black.
Barracuda Gran Coupe had a textured Argent Silver tail panel as standard.
The tail lights themselves are painted to match the tail panel area, so a `Cuda with a Organosil tail panel would have matching Organosil Black Tail light surrounds, a Barracuda would have body colour tail light surrounds, and a Gran Coupe would have Textured Argent Silver tail light surrounds,
ALL the tail light trim bright work (chrome) stays chrome on every model Barracuda, Gran Coupe and `Cuda.
The side markers are painted body colour front and back, the exception to the rule is when a Billboard is applied (1971 only), then the rear side marker is colour matched to the Billboard colour, say you have a Black Billboard on a White car - the front side marker would be White and the rear side marker with in the Black Billboard will be Black.
That means on a Black painted car like yours, if you are applying a Flat Black Billboard, then the side marker will also be Flat Black to match the Billboard.I hope this discription helps you out